Bile acids and/or by-products as a result of bacterial degradation are believed to be related to large bowel carcinogenesis. Cholecystectomy has been shown to alter bile acid metabolism. A retrospective study involving 706 cases of large bowel cancer grouped by subsite, sex, and age, identified during the Third National Cancer Survey was recently completed. Thirty-eight of 291 patients (13%) with cancer of the ascending or transverse colon (right-sided large bowel cancer) had hospital records indicating a history of prior cholecystectomy as compared to 26 of 415 patients (6.3%) with descending, sigmoid, or rectal cancer (left-sided large bowel cancer). When comparing right-sided large bowel cancer patients with left-sided large bowel cancer patients, the estimated relative risk was found to be 2.23 with 9% confidence limits of 1.33 to 3.75. Although the results are significant, a possible bias associated with review of hospital records could account for this relationship. Therefore, we are currently replicating this study and validating prior history of cholecystectomy in hospital records. Operative notes and X-rays have been reviewed to validate the absence or presence of the gallbladder at time of colon cancer surgery. Interviews with the surgeon and/or family are also being conducted. Finally, a neighborhood control group is also being interviewed.